Liquified gases (LGs) are used in a wide variety of applications. Perhaps the most common use of liquified gas is the use of liquified propane gas (LPG) from relatively small tanks in gas grills, mobile homes, and the like, where LPG is typically dispensed into tanks for localized use from larger municipal or commercial sources.
The handling of LPG can be hazardous due to the combined dangers of handling material that is both dispensed under pressure and flammable.
As well as the safe handling of LPG, it is typically necessary to be able to measure the amount of gas dispensed. This task is often complicated by the effects of ambient temperature, etc. on the accuracy of such measurements. Dispensing LPG under relatively cool temperatures followed by the transfer of the LPG tank to a relatively warmer environment can cause a tank to rupture or discharge gas through an over-pressure valve. This effect can be exacerbated by the inaccurate measurement of LPG upon filling, which can leave a substantial volume of the tank left filled with gas subject to the effects of Charles Law. In contrast, allowing fill to continue until the tank is full creates the risk of valve rupture or over-pressure release. Thus, accurately and safely minimizing gas space in an LPG tank is desirable so as to reduce or eliminate the described hydrostatic effect.
Presently, common practice is to fill tanks and measure the gas by weight, while knowing the density of the LPG. This technique is prone to error and thus does not consistently result in a given tank being charged to capacity while minimizing gas space in the tank.
Gas discharge not only poses the danger of ignition and fire or explosion, it also creates a form of air pollution by the release of organic volatiles into the atmosphere.
Strictly mechanical devices, using floats and seals, have been applied to the present problem, but these devices can have high failure rates.
Accordingly, it is desirable to be able to safely, accurately and reliably dispense and measure LPG into a tank container while minimizing the gas space left in the charged tank.
Although described against the backdrop of problems associated with LPG, it will be understood that the present invention may be applied to the dispensing and measurement of any LG.
In view of the present disclosure or through practice of the present invention, other advantages, or the solution to other problems, may become apparent to one of ordinary skill.